2011 SuperDARN Workshop
ABSTRACTS

abstract.
The term "Medium Scale Traveling Ionospheric Disturbance" (MSTID) can refer
to at least two distinct proposed phenomena: 1. a thermospheric acoustic
gravity wave that causes density and height variations in the ionosphere via
collisional and density/ionization effects; or 2. an electrified structure due
to a plasma instability related to the model presented by Perkins. In this
work, we present examples of the signatures of both kinds of structures in
SuperDARN backscatter data. Finally, we comment on observational support
for the recent theory of Kelley that the so-called "Perkins orientation" of
electrified MSTIDs is due to minimization of Joule damping as gravity waves
reach the middle latitudes.